Development of the Skeleton Flashcards

1
Q

Skull - Parts? Role?

A

Neurocranium - forms protective case

Viscerocranium - skeleton of the face

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2
Q

Membranous neurocranium - Roles? Development? Bone names? Key characteristics? Fontanelles?

A

Membranous neurocranium:

  • roof and sides of the skull develops from the neural crest cells
  • undergo membranous ossification from flat bones
  • surrounds the brain and sensory organs (calvaria)
  • formed by the parietal, frontal, temporal and occipital bone
  • calvaria has no cartilage
  • direct ossification of mesenchyme
  • fibrous sutures
  • allow distortion to pass birth canal
  • allow brain growth
  • fontanelles: 6, posterior at 3m and anterior at 18
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3
Q

Cartilagenous neurocranium - 2 Parts? Roles? Development? Bone names? Key characteristics? Fontanelles?

A

Prechondral chondrocranium:
- in front of pituitary gland, derived from neural crest
Chordal chondrocranium:
- posterior to pituitary and arise from paraxial mesoderm

Fuse and ossify by endochondral ossification to form skull base

Cranial base:
- occipital bone, sphenoid, ethmoid, petrous, mastoid part of temporal bones

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4
Q

Viscerocranium - overview? development? pharyngeal arches?

A

Overview:

  • consists of bones of the face
  • formed mainly from first 2 pharyngeal arches
  • 5 pharyngeal arches (1,2,3,4,6); developing in craniocaudal sequence, 1st pair 22d, 2nd/3rd pair 24d and 2th/6th pair 29d
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5
Q

Cephalogenesis - early chordates?

A

Early chordates:

  • notochord for support
  • simple NS
  • segmented muscle blocks
  • branchial clefts
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6
Q

Cephalogenesis - first vertebrates? skull formation?

A

Skull formation: Jaw less

  • occipital and parachordal cartilages appeared to support notochord in head
  • cartilagenous capsules protect sense organs
  • branchial arches supported by cartilagenous rods
  • cartilage 0 migrates to the head, so 2nd arch cartilage become 1st
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7
Q

Cephalogenesis - first vertebrates (with jaw)?

A

Skull formation: jaw

  • modification of first arch cartilage
  • palatopterygoquadrate bar became upper jaw
  • Meckel’s cartilage became the lower jaw
  • fibrous connection between them was the TMJ
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8
Q

Cephalogenesis - vertebral evolution?

A

Vertebral evolution:

  • brought massive expansion in head
  • protecting the brain with additional bont skeletal elements were developed
  • from the neuroectoderm, from which neural crest cells migrate and differentiate into ectomesenchyme
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9
Q

Skull development - signalling molecules/genes?

A

Development:

  • Hox gene play key role in craniofacial development
  • pharyngeal arches rely on Hox gene expression
  • Calvarial growth an cranial suture morphogenesis is regulated by MSX1/2, shh, BMPs, TGF and FGFRs
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10
Q

Newborn skull’s fontanelles - location? fuse dates?

A
Anterior fontanelle:
- between frontal and parietal bones
- fuses by age of 2
Posterior fontanelle:
- between parietal and occipital bones
- fuses by 2-3 months
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11
Q

Newborn skull - comparison to adult skull?

A

Facial skeleton 1/8 compared to 1/3 adult skull

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12
Q

Newborn skull - development?

A

Development:

  • frontal bone (in 2 halves), suture obliterated in 8th year, can persist as metopic suture
  • mastoid and styloid processes absent, facial nerve close to surface at birth (forcep injury)
  • palpation of ant. and post. fontanelles, progress of growth of frontal and parietal bones, degree of hydration and level of intracranial Pa
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13
Q

Post-natal period - neonatal period? growth period?

A

Neonatal period:
- most major bones ossified, but can move relative to another
Growth period:
- sutures permit growth at edges of flat bones

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14
Q

Spheno-occipital synchondrosis - overview?

A

Overview:

  • allows anterior/posterior growth of skull
  • closes at 20
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15
Q

Development of the Head - embryonic period? foetal period? post-natal period?

A
Embryonic period:
- pharyngeal arches
- facial development
- ossification centres
Foetal period:
- continued ossification
Post-natal period:
- closure of fontanelles
- facial and skull vault growth
- sinus expansion
- suture fusion
- teeth eruption
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16
Q

Cranial sutures - names?

A
Metopic/Frontal suture
Sagittal suture
Coronal suture
Lambdoid suture
Squamosal suture
17
Q

Facial sutures - names?

A
Intermaxillary
Nasomaxillary
Internasal
Nasofrontal
Zygomaxillary
Zygotemporal
Frontozygomatic
Frontomaxillary
18
Q

Cranial vault growth - overview? problems? development? completion?

A

Overview:
- vault growth directly related to brain development
Problems:
- brain development affect growth of skull and vice versa
Development:
- rapid growth between birth to seven (vault size rapid during first year)
Completion:
- about age 2

19
Q

Craniosynostosis - definition? non-syndromal craniosynostosis? syndromal craniosynostosis?

A
a disorder that involves 
Definition:
- premature fusion of the cranial vault sutures causing abnormal and disproportionate growth of the cranial bones during development 
Non-syndromal:
- Scaphocephaly (sagittal)
- Plagio (unicoronal)
- Trigono (metopic)
- Brachy (bicoronal)
Syndromal: autosomal dominant
- Crouzon
- Apert
- Carpenter
- Pfeiffer
Symptoms:
- increased intracranial Pa and developmental delay
- multiple operations needed
20
Q

Role of sutures?

A
  • Allow for growth of the cranium
21
Q

Neurocranium definition?

A
  • Series of 8 bones, which are flat, curved and united by fibrous interlocking sutures
22
Q

Viscerocranium definition?

A
  • 14 irregular bones

- Maxilla and mandible

23
Q

General bones of the skull?

A
  • Frontal
  • Parietal
  • Sphenoid
  • Nasal
  • Lacrimal
  • Occipital
  • Zygomatic
  • Maxilla
  • Mandible
24
Q

Bird’s eye view of the cranium - annotated diagram?

A
  • Frontal bone
  • Coronal suture (bregma)
  • Sagittal suture (bregma and Lambda)
  • Parietal bone
  • Parietal foramen
  • Lambdoid suture (lambda)
  • Occipital bone
25
Skull features - view below?
- Incisive fossa (nasopalatine LA) - Palatine process of maxilla - Palatine bone - Sphenoid - Foramen (lacerum, ovale, spinosum) - Carotid canal - Stylomastoid foramen
26
Skull differences between adult and child?
- Anterior fontanelle - Posterior fontanelle - Sphenoid fontanelle - Mastoid fontanelle
27
Skull characteristics - At birth?
``` Facial skeleton: - 1/8 of skull Frontal bone: - 2 halves (suture - metopic after 8th year) Mastoid and styloid processes are absent ```
28
Sinuses - Where are they located?
``` Frontal bone: - sinuses above the eye socket - irregular shaped Maxillary: - either side of the nose ```
29
Facial skeleton - variability? constituents?
``` Variability: - thickness Constituents (thick cortical): - cranium, nasal bone, zygomatic bone, orbital rim and zygomatic buttress Maxilla sinus is thin ```
30
Midfacial skeleton - characteristic?
Characteristics: - increased SA to bone-vol ratio, with closer prox to BV providing superior supply of nutrients and promotes increased healing rate
31
Zygoma - role? fracture?
Role: - protection of globe of the eye, origin to masseter muscle and transmit masticatory forces Blow-out fracture: - involving infraorbital nerve, inferior rectus and inferior oblique muscle
32
Rene Le Fort classification - types?
I: - only the maxilla - from the maxilla to the nasal bone - across the facial skeleton
33
Nasal bones - characteristics? shape? role?
``` Characteristics: - thick (bridge area) Shape: - triangular with septum Role: provides strength, considerable resistance to direct blow - cribriform bone may fracture ```
34
Mandible - annotations (outer and inner) and fractures?
``` Annotations: Outer - body - ramus - condylar process - oblique line - mental foramen - inferior and superior border - superior surface Annotations: Inner - head/neck of condylar - angle - pterygoid fovea - mandibular notch - coronoid process - mandibular foramen - mylohyoid groove - retromolar triangle - attachment for pterygomandibular raphe Fractures: - body - symphysis - angle - ramus - subcondylar and condylar - coronoid process ```
35
Mandible and fracture relation? Fracture location?
Mainly in the maxillofacial area: - fracture force - morphology - strength and resilience of mandible and attached muscles Symphysis: - thickest and strongest Incisor region: - oblique due to actions of genial and mylohyoid muscles (fragments with incisor teeth overlap) Canine region: - weak due to length Angle region: - indirect force - weak due to right angle and wisdom teeth - fragments displaced due to opposing effects of pterygomasseteric sling and suprahyoid musc Inferior dental bundle: - fibrous sheath protect vessels and nerves Multifact blood supply: - endo/periosteum and musc Condylar: - contusion, dislocation or intra/extracapsular fractures (displaced medially due to resistance of strong lateral ligaments, deviates to injured side on opening)
36
Edentulous mandible - blood supply? changes?
Blood supply: - only periosteal supply - if stripped for plating result in non-union fractures Changes: - reduct in alveolar ridges - due to resorption after tooth loss - rapidly in first year (mandible > maxilla) - lack bulk of bone and structures such as inferior alveolar nerve and mental foramen (implants) - reduced retromolar area (implant) - sclerotic bone (poor screw anchorage)